"Minor fatty compounds" designates all non-glyceride fatty constituents which occur in natural fatty substances They may be steroids, especially sterols, fatty alcohols, fat-soluble vitamins, pigments, hydrocarbons, free fatty acids, abietic and pimaric acids, flavouring compounds and the like.
For more detail, reference can be made to the definition given in Manuel d'analyse des corps gras (Manual of the analysis of fatty acids)" JP WOLF--Ed Azoulay--Paris 1969, pages 11 and 25 .
Within the context of the present invention, the term "steroids" designates all compounds containing a more or less hydrogenated cyclopentanophenanthrene skeleton. Many of these compounds are alcohols and are termed sterols. They may occur in the form of esters especially of fatty acids, commonly designated by the term "cerides".
Cholesterol belongs to the sterol family. It has been known for some time that it is the main constituent of biliary calculi. Its reputation has recently been strengthened by its involvement in circulatory disorders, and more particularly the hardening of the arteries.
Nonesterified cholesterol is the main constituent of fatty substances of animal origin. These animal fats, which are present in most of our foodstuffs, constitute an important source of cholesterol which, in the event of an excess, may be the cause of serious cardiovascular diseases including myocardial infarction in particular.
Fatty substances of plant origin contain not cholesterol but phytosterols whose structure is very similar to it, such as for example: .beta.-sitosterol, campesterol, stigmasterol, brassicasterol, .DELTA.-7-stigmasterol, .DELTA.-5-campesterol, .DELTA.-5-avenasterol, .DELTA.-7-avenasterol, .DELTA.-7-9-sigmatadienol, fucosterol or ergosterol.
The process according to the invention also applies to the oxidised derivatives of steroids: sterones. These compounds occur especially in frying oils used repeatedly. Their presence in food products is not desirable as they are not devoid of toxic effect.
In addition, steroids are products of high added-value both economically and technically. Indeed, they have the potential of constituting high grade raw materials for the preparation of vitamin compounds (ergosterol: vitamin D2) or hormonal compounds (equilenin, oestrone, progesterone, testosterone or cortisone and the like). In addition to their pharmaceutical applications, steroids, and more particularly sterols and their fatty acid esters (cerides), may be used in the cosmetics industry as emulsifiers.
As far as the other minor fatty compounds are concerned, there may be distinguished, on the one hand, compounds which are undesirable from the food or technological point of view such as free fatty acids which promote oxidation, degradation compounds such as polymerised acids, foul-smelling compounds, colouring substances and savoury substances and the like; and on the other hand, compounds of high food or technological value such as fat-soluble vitamins, essential fatty acids (linoleic acid, .alpha.-linoleic acid, .gamma.-linoleic acid, arachidonic acid, DHA and EPA), rare fatty acids (ricinoleic and abietic acids), and flavouring compounds.
There are thus several justifications for all the technological developments designed to extract the minor fatty compounds from fatty biological substances. This term designates in particular, on the one hand, animal fats, what they are storage fats such as fish oils or animal oils (tallow, chicken fat, lard and the like), structural fats such as those present in muscular, placenteral or nerve tissue (meat, egg, spinal cord, brain and the like) or fats from glandular secretion such as milk fats, or fats from skin secretion such as cerides (lanolin); and, on the other hand, vegetable fats. Finally, the fats may be a mixture of animal fats and vegetable fats such as margarines.